Highly miniaturized sensors with the assistance of which pressure differences or pressure fluctuations can be measured are desired for various applications. An employment as a relative pressure sensor for measuring pressure difference comes into consideration, for example, when the relative pressure of a gas enclosed in a first volume is to be identified, compared to a gas enclosed in a second volume. In such a case, it is possible to separately measure the two pressures that prevail in the gas volumes and to compare these absolute measurements to one another. However, the measurement takes on an especially simple and expedient form when the same pressure sensor is in communication with both gas volumes, and an existing pressure difference thus has an immediate effect on the measured values supplied by this sensor.
Another possible employment for such a sensor is the measurement of brief-duration pressure fluctuations, particularly for acoustic waves, for which the sensor then represents a sound transducer, i.e. a microphone, for the conversion of the acoustic waves into electrical signals. Microphones have been manufactured as micromechanical components in silicon for approximately 12 years. An overview of the development is contained in the overview article by P. R. Scheeper et al., "A Review of Silicon Microphones" in Sensors and Actuators A 44, 1-11 (1994). When the electronic components provided for the drive circuit of the microphone are manufactured in the framework of a CMOS process, it is advantageous when the micromechanical components of the microphone are also manufactured compatible with this process. When a capacitative measurement of the electrically conductive microphone membrane relative to a cooperating electrode firmly arranged on a chip is provided for the microphone, two chips connected to one another have hitherto been employed. The micromechanical sensor structure with the membrane is located on the one chip; the cooperating electrode is arranged on the other chip. Such a microphone is described, for example, in the publication by T. Bourouina et al., "A new condenser microphone with a p.sup.+ silicon membrane" in Sensors and Actuators A.31, 149-152 (1992).
A problem that results in micromechanical microphones is that small membranes can only be weakly deflected and therefore exhibit a low sensitivity to air pressure fluctuations. Moreover, the air between the measuring electrodes represents a great damping of the membrane because the air cannot be quickly and highly enough compressed. As a result thereof, the sensitivity of the microphone is reduced. It is therefore necessary to enable a pressure equalization of the air between the measuring electrodes.